1. Field of the Invention
The invention generally relates to an apparatus for generating a selected sequence of data bits and, more particularly, to an apparatus for generating the C block in AES/EBU formatted data.
2. Description of Prior Art
One format for the serial transmission of digital audio data is called the AES/EBU format. With reference to FIG. 1, the AES/EBU format comprises individual frames transmitted at a selected sampling frequency. Each frame is comprised of two sequential sub-frames, Sub-frame A and Sub-frame B, with each sub-frame comprising 32 bits. The 32 bits of the sub-frame are divided into 4 Sync bits, 4 Auxiliary bits, 20 bits of Audio data, an Audio Sample Validity bit V, a User bit U, a Channel Status bit C, and a Parity bit P.
The frames of data are transmitted in blocks comprised of 192 frames. A C block is composed of all of the C bits in the 192 frames of a block and together comprise 24 bytes. The function of the C block is to transmit information about the format and about other system parameters. For instance, bits 6 and 7 of byte 0 in the C block indicate to a receiver of the AES/EBU formatted data whether the sampling frequency is 48 kHz, 44.1 kHz, or 32 kHz. Also, bits 2 to 4 of byte 0 indicate the type of emphasis: manual emphasis, no emphasis, CD emphasis, or CCITT emphasis. Therefore, the C block transmitted by a particular apparatus will vary depending upon the exact set-up of the audio system.